Fluid supply systems use motors to drive pumps and transfer fluids from supply reservoirs, such as wells, to demand reservoirs, such as tanks. A sensor measures a characteristic of the fluid, and a motor controller controls operation of the motor. A motor controller may operate the motor at a constant speed. When pressure reaches a low pressure limit, the motor controller turns on the motor and keeps the motor running until pressure reaches a high pressure limit, at which time the motor controller turns the motor off. The difference between the high and low pressure limits can be about 20 PSI. If the motor controller is a constant speed controller, then the motor runs at a speed determined by the frequency of the line voltage powering the motor controller.
The pressure variation generated by a control system with a constant speed controller can be detrimental. For example, the pressure variation affects how long it takes to fill a dish-washer or clothes-washer in a home. Near the high pressure the filling cycle is quicker than near the low pressure. Pressure variation is also undesirable in irrigation systems, because the reach of the irrigation heads depends on water pressure. As pressure decreases, the reach of the irrigation head is reduced. To compensate for the reduction additional irrigation heads may be added, increasing cost and resulting in overwatering of some areas to ensure proper watering of others, which wastes water.
It is desirable to replace constant speed controllers with variable speed controllers to reduce pressure variation and improve performance of the water supply system. However such replacement requires labor to remove the old controller and install the new controller, which can dissuade owners from switching controllers. Accordingly it is desirable to improve motor controllers to facilitate upgrades without incurring labor costs and complexity that may dissuade owners from performing the upgrades.
The background to the disclosure is described herein, including reference to documents, acts, materials, devices, articles and the like, to explain the context of the present invention. This is not to be taken as an admission or a suggestion that any of the material referred to was published, known or part of the common general knowledge in the art to which the present invention pertains, in the United States or in any other country, as at the priority date of any of the claims.